Research And Application Of GPS Leveling Model

At present, GPS positioning technology has been widely applied in survey work, mainly reflected in the control network, control network of city and engineering surveying control network, large scale digital mapping, cadastral surveying, deformation observation, the digital city construction and precise engineering surveying in aspects of establishing the national plane at all levels, in the specific application highlights its positioning accuracy high, all-weather operation advantage. But because the existing technical measures are difficult to obtain more precise geoid results, so GPS cannot be converted to the determination of the geoid height actual mapping work in normal high, difficult to play the role of elevation control. Therefore, how to effectively apply the geodetic height into normal height, direct services of Surveying and mapping production, namely can use GPS observations of fast, efficient to obtain three-dimensional coordinates, is a very practical and meaningful subject.Based on the analysis of research and application status of GPS level elevation at home and abroad in recent years, with Liaoyuan southern new town as the experimental zone, using GPS observation data in combination with geometric leveling data, GPS elevation fitting research and test were carried out, research achievements as follows:(1) For GPS level elevation fitting, it is necessary to give full consideration to precision effect of the known point location.the precision of unknown points depends largely on the distribution of known points, so when making GPS level elevation fitting, the known points must be distributed evenly over the whole test area, which should have certain representativeness.(2) Study high-precision quasi-geoid model suitable for the region, with quasi-geoid,determine height anomaly so as to convert the geodetic height measured by GPS to normal height, thus replacing leveling.(3) GPS elevation fitting is made with methods such as first-degree surface, quadric surface and polyhedral function, both internal and external precision of the quadric surface meet the requirements, and the calculation process is simple, occupying less machine-hour, and the calculation results are relatively stable, so you can think the quadric surface model is the best.(4) After selecting the right fitting model, the fitting precision can reach fourth –grade leveling, and meet detail elevation control of general engineering. For control survey, fitting data and actual measured data can be tested mutually for easily finding the mistake.